Cycloidal Pinwheel Pair with Uniform Contact and One-tooth Difference

ABSTRACT

Disclosed is a cycloidal pinwheel pair with uniform contact and one-tooth difference, comprising a stator and a rotor. Each gear tooth profile of the rotor has a modified recess provided symmetrically on both sides; the starting point (A) of the modified recess on one side of the gear tooth profile is located between a first point and a second point determined by locations of two limit positions, the end point (B) of the modified recess on the same side of the gear tooth profile is located between a third point and a fourth point determined by locations of two limit positions. By adopting the present disclosure, the internal leakage formed between high and low pressure chambers is effectively avoided, thereby significantly improving the volume efficiency and mechanical efficiency. Meanwhile, the present disclosure is extremely simple in structure and can be molded by one-time grinding with better manufacturability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Application No. 201110378546.7, “Cycloidal Pinwheel Pair with Uniform Contact and One-tooth Difference”, filed on Nov. 24, 2011, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a cycloidal pinwheel pair, and more particularly to a cycloidal pinwheel pair with uniform contact and one-tooth difference, belonging to the technical fields of cycloidal hydraulic motors and fully hydraulic diverters.

BACKGROUND ART

A cycloidal pinwheel pair with one-tooth difference has advantages such as compact structure, high kinematic precision, low noise, high tooth strength, strong bearing capacity, little junction surface friction, high transmission efficiency, higher power density, and so on. Therefore, it is widely used in products such as cycloid hydraulic motors with large torque and low speed, fully hydraulic diverters, cycloid pumps, and so on.

As shown in FIG. 1 and FIG. 2, there are mainly two configurations when the meshing pair movement of the cycloidal pinwheel pair with one-tooth difference is applied for hydraulic transmission. FIG. 1 shows a configuration of independent pinwheel teeth, and FIG. 2 shows a configuration of integrated pinwheel teeth, wherein, 01 represents the stator, 02 represents a cycloidal pinwheel which works as the rotor, and 03 represents the pin tooth on the stator. The cycloidal pinwheel contacts to all pin teeth in the meshing pair movement of the cycloidal pinwheel pair with one-tooth difference, thereby forming independent chambers which, in theory, are sealed with zero-clearance therebetween. However, since machining errors and position errors exist in mechanical parts, a certain clearance has to be reserved in design to compensate the errors afore-mentioned; therefore, every independent chamber is sealed by oil film in actual. In situations of heavy load or large torque transmission, the above mentioned errors and the reserved clearance may cause internal leakage of the cycloidal meshing pair (such as the hydraulic motor), which significantly affects the working stability of hydraulic equipment such as the hydraulic motor, and reduces the volume efficiency and mechanical efficiency.

The US patent U.S. Pat. No. 7,481,633 disclosed a cycloidal pinwheel pair with modified profile, wherein, the original cycloidal profile of the cycloidal pinwheel is modified to have discontinuous concaves according to a certain regularity, so that in the transmission process when the cycloidal pinwheel is meshing with the pin teeth of the stator, the errors are compensated by the concaves instead, without the need of reserving the clearance. Its advantage is that the concave segments can only enable communication between adjacent chambers having similar hydraulic pressure, without causing internal leakage between chambers having larger pressure differentials; therefore, it is benefit for keeping the operation steady and for improving the volume efficiency and mechanical efficiency. Moreover, after the cycloidal pinwheel is modified, the meshing contact of the cycloidal pinwheel is decreased, which is benefit for reducing the transmission resistance and hydraulic pulsation. However, this technical solution employs too many concave segments, as a result, it is complex in structure, tedious in design and calculation, and difficult to produce.

SUMMARY OF THE INVENTION

In view of the defects existing in the prior art, an object of the present disclosure is to provide a cycloidal pinwheel pair with uniform contact and one-tooth difference, which is capable of avoiding internal leakage, improving volume efficiency and mechanical efficiency, and which has simple structure and better manufacturability, on the premise of maintaining the original structure parameters of the cycloidal pinwheel pair of hydraulic components unchanged.

Researches show that, when the cycloidal pinwheel pair is in movement (as shown in FIG. 3A), gear teeth of the rotor are continuously meshing with pin teeth, and the cycloidal curves of the gear teeth and the pin teeth are continuously rolling relatively, the meshing contact points are continuously changed along with the movement of the cycloidal pinwheel pair. The meshing instant center P is the intersection point of the connection lines respectively formed between each of pin tooth centers o1, o2, o3, o4, o5, o6 and o7, and the respective one of theoretical contact points 11, 12, 13, 14, 15, 16 and 17 of the gear teeth, and the meshing instant center is also the meshing pitch point of the gear teeth and the pin teeth. The motion trail of the meshing instant center is a circle which takes the rotor center “o” as the center of the circle, and takes the product (7×e) of the number of pin teeth and the eccentricity of the rotor as the radius of the circle. In one transmission cycle, each of the pin teeth has two specific positions. Taking the pin tooth having the center o5 as an example, one specific position is the position where the center o5 is nearest to the meshing instant center P (as shown in FIG. 3A); at this position, the pin teeth, whose centers are farthest to the meshing instant center P, are two symmetrically distributed pin teeth whose centers are o1 and o2; the intersection point 11, formed by the connection line from the meshing instant center P to the center o1 of the farthest pin tooth and by the profile of the corresponding gear tooth meshing with the pin tooth whose center is o1, is the meshing point at this position; and the intersection point 16, formed by the connection line from the meshing instant center P to the center o6 of the adjacent pin tooth and by the profile of the corresponding gear tooth meshing with the pin tooth whose center is o6, is the meshing point at this position. The other specific position is the position where the center o5 is farthest to the meshing instant center P, at this position, the pin teeth, whose centers are nearest to the meshing instant center P, are symmetrically distributed pin teeth whose centers are o1 and o2; the intersection point 22, formed by the connection line from the meshing instant center P to the center o2 of the nearest pin tooth and by the profile of the corresponding gear tooth meshing with the pin tooth whose center is o2, is the meshing point at this position; and the intersection point 26, formed by the connection line from the meshing instant center P to the center o6 of the adjacent pin tooth and by the profile of the corresponding gear tooth meshing with the pin tooth whose center is o6, is the meshing point at this position.

In order to realize the object mentioned above, the present disclosure provides a cycloidal pinwheel pair with uniform contact and one-tooth difference, comprising a stator having pin teeth in interval distribution, and a rotor having gear teeth meshing with the pin teeth of the stator, and each gear tooth profile of the rotor has a modified recess provided symmetrically on both sides; wherein,

a starting point of said modified recess on one side of the gear tooth profile is located between a first point and a second point: when a predetermined pin tooth locates nearest to a meshing instant center, a first meshing point, formed by a pin tooth locating farthest to said meshing instant center and a corresponding gear tooth meshing therewith on a same side, is the first point; and when the predetermined pin tooth locates farthest to said meshing instant center, a second meshing point, formed by an adjacent pin tooth and a corresponding gear tooth meshing therewith on a same side, is the second point;

an end point of the modified recess is located between a third point and a fourth point: when the predetermined pin tooth locates nearest to said meshing instant center, a third meshing point, formed by an adjacent pin tooth and a corresponding gear tooth meshing therewith on the same side, is the third point; and when the predetermined pin tooth locates farthest to said meshing instant center, a fourth meshing point, formed by a pin tooth locating nearest to the meshing instant center and a corresponding gear tooth meshing therewith on the same side, is the fourth point.

Experiments indicate that it is optimal when the starting point of the modified recess is located midway between the first point and the second point, and the end point of the modified recess is located midway between the third point and the fourth point.

Preferably, said modified recess is an equi-depth recess of gear tooth profile of a standard cycloidal pinwheel, and a depth of said modified recess is between 0.03 mm and 0.008 mm, preferably 0.012 mm.

By adopting the present disclosure, in the transmission process, the adjacent high pressure chambers communicate with each other, and the adjacent low pressure chambers also communicate with each other, thereby forming a transition chamber between the high pressure chamber and the low pressure chamber to realize pressure transition. Since the present disclosure adopts the modified recess to replace the conventional clearance designed for error compensation, the internal leakage formed between high and low pressure chambers is effectively avoided, thereby significantly improving the volume efficiency and mechanical efficiency. Meanwhile, the present disclosure is extremely simple in structure and can be molded by one-time grinding with better manufacturability. Moreover, at the meshing clearance generated by the modified recess on the high pressure chamber and on the low pressure chamber, oil film filled with hydraulic oil is formed, which is benefit for reducing the friction of the kinematic pair, improving the flexibility of the movement, and reducing the requirement of machining precision.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be described in further details with the accompanying drawings.

FIG. 1 is a schematic diagram illustrating the configuration of independent pinwheel teeth in the prior art;

FIG. 2 is a schematic diagram illustrating the configuration of integrated pinwheel teeth in the prior art;

FIG. 3A and FIG. 3B are status diagrams illustrating the two limit positions according to one embodiment of the present invention; wherein, • represents the center of the stator;

o' represents the center of the rotor;

P represents the meshing instant center (meshing pitch point);

o1, o2, o3, o4, o5, o6, o7 respectively represent the centers of the pin teeth (centers of the chambers);

11, 12, 13, 14, 15, 16, 17, and 22, 23, 24, 25, 26, 27 respectively represent the theoretical meshing contact points;

A, B, C, D respectively represent the profile modified points;

FIG. 4 is a structure diagram illustrating the profile modified cycloidal pinwheel according to one embodiment of the present disclosure;

FIG. 5 is a partial enlarged diagram illustrating the profile modified line AB formed by connecting the profile modified points A and B;

FIG. 6 is a schematic diagram illustrating hydraulic pressure chambers formed at a certain movement moment, illustrating the stator 01, the rotor 02, the pin teeth 03, and the hydraulic pressure chambers Q1, Q2, Q3, Q4, Q5, Q6 and Q7 formed by the meshing points, according to one embodiment of the present disclosure.

PREFERRED EMBODIMENTS OF THE INVENTION

Embodiment one:

The structure of the cycloidal pinwheel pair with uniform contact and one-tooth difference according to embodiment one is as shown in FIG. 3A and FIG. 3B, including the stator 01 having seven pin teeth 03 in interval distribution, and the pinwheel rotor 02 having six gear teeth meshing with the stator, the centers of the seven pin teeth respectively are o1, o2, o3, o4, o5, o6 and o7. The meshing instant center P is the meshing pitch point formed by the rotor and the pin teeth, and is also the intersection point of the connection lines respectively formed between each of pin tooth centers o1, o2, o3, o4, o5, o6 and o7, and the respective meshing contact points 11, 12, 13, 14, 15, 16 and 17 of the gear teeth. Each gear tooth profile of the pinwheel rotor has a modified recess provided symmetrically on both sides (as shown in FIG. 4).

As shown in FIG. 4, the starting point A of the modified recess on one side of the gear tooth profile is located between the first point 11′ and the second point 26′ which are determined by following methods: when the predetermined pin tooth having the center o5 locates nearest to the meshing instant center P, as shown in FIG. 3A, the first meshing point 11, formed by the pin tooth having the center o1, locating farthest to the meshing instant center P, and a corresponding gear tooth meshing therewith on a same side, is the first point 11′, that is, the point 11 is displaced to the corresponding point 11′ of each gear tooth; and when the predetermined pin tooth having the center o5 locates farthest to the meshing instant center P, as shown in FIG. 3B, the second meshing point 26, formed by an adjacent pin tooth having the center o6 and a corresponding gear tooth meshing therewith on a same side, is the second point 26′, that is, the point 26 is displaced to the corresponding point 26′ of each gear tooth. The starting point A of the modified recess is optimally located midway between the first point 11′ and the second point 26′.

As shown in FIG. 4, the end point B of the modified recess on the same side of the gear tooth profile is located between the third point 16′ and the fourth point 22′ which are determined by following methods: when the predetermined pin tooth having the center o5 locates nearest to said meshing instant center P, as shown in FIG. 3A, the third meshing point 16, formed by the adjacent pin tooth having the center o6 and a corresponding gear tooth meshing therewith on the same side, is the third point 16′, that is, the point 16 is displaced to the corresponding point 16′ of each gear tooth; and when the predetermined pin tooth having the center o5 locates farthest to said meshing instant center P, as shown in FIG. 3B, the fourth meshing point 22, formed by the pin tooth having the center o2, locating nearest to the meshing instant center P, and a corresponding gear tooth meshing therewith on the same side, is the fourth point 22′, that is, the point 22 is displaced to the corresponding point 22′ of each gear tooth. The end point B of the modified recess is optimally located midway between the third point 16′ and the fourth point 22′.

Since each gear tooth profile of the rotor has the symmetrical modified recesses on both sides, the modified recess on the other side can be determined once the modified recess on one side is determined.

In order to simplify the process, the modified recess is an equi-depth recess of gear teeth profile of a standard cycloidal pinwheel, the depth of the modified recess is between 0.03 mm and 0.008 mm, and an optimal depth is 0.012 mm. Preferably, the transition between the bottom of the modified recess and the starting point A, and the transition between the bottom of the modified recess and the end point B, are both smooth arc transitions (as shown in FIG. 5).

During operation as shown in FIG. 6, when the cycloidal pinwheel pair is on a certain operative condition, the chamber Q1 is on pressure alternating status, namely a high-low pressure alternating status; and the chambers Q2, Q3 and Q4 are on the same pressure status (such as low pressure), while the chambers Q5, Q6 and Q7 are also on another same pressure status (such as high pressure). Each of gear teeth has the modified recesses determined by the method mentioned above, therefore under this position status (as shown in FIG. 3A), the cycloidal pinwheel pair with uniform contact and one-tooth difference only has three meshing points which are 11, 12, 15, thereby chambers with the same pressure status communicate with each other, forming the so-called cycloidal pinwheel pair with uniform contact and one-tooth difference, which actually is a modification relative to the status in the prior art that seven pin teeth contact with six gear teeth respectively at the same time. Similarly, the cycloidal pinwheel pair with uniform contact and one-tooth difference, under other status, always has two series of communicated chambers, each series of chambers are formed by three chambers having the same pressure status, and the remaining single chamber is a high-low pressure status alternating chamber.

The cycloidal pinwheel pair with uniform contact and one-tooth difference always maintains three-point meshing contact in movement, therefore, its movement is more flexible and the stress is more steady; and the oil film is formed between the adjacent chambers, thereby improving the pressure bearing capacity between meshing pairs, which is beneficial for improving the stress distribution in movement. Moreover, the present disclosure adopts the modified recess to replace the conventional clearance designed for error compensation, thereby dramatically reducing the internal leakage which easily occurs between high and low pressure chambers when the loading capacity is too high in the prior art, thereby significantly improving the volume efficiency and the mechanical efficiency. Experience has proven that, according to the cycloidal pinwheel pair with uniform contact and one-tooth difference of this embodiment, the machining process of the rotor is simpler, the meshing movement is more flexible, thereby improving the efficiency, and prolonging the life time. By adopting the present disclosure, the production cost is reduced, and the overall reliability of the product is improved.

In addition to the embodiment mentioned above, the present disclosure may have other implementation manners, for example, the teeth number of the cycloidal pinwheel pair may be 5 pin teeth with 4 gear teeth, or more; and the configuration of the cycloidal pinwheel teeth may be either assembled or integrated, and so on. Various modifications and replacements may be made therein without departing from the theory of the present disclosure, which should also be seen in the scope of the present disclosure. 

What is claimed is:
 1. A cycloidal pinwheel pair with uniform contact and one-tooth difference, comprising a stator with pin teeth in interval distribution, and a rotor having gear teeth meshing with the pin teeth of said stator, and each gear tooth profile of the rotor has a modified recess provided symmetrically on both sides; wherein, a starting point of said modified recess on one side of the gear tooth profile is located between a first point and a second point: when a predetermined pin tooth locates nearest to a meshing instant center, a first meshing point, formed by a pin tooth locating farthest to said meshing instant center and a corresponding gear tooth meshing therewith on a same side, is the first point; and when the predetermined pin tooth locates farthest to said meshing instant center, a second meshing point, formed by an adjacent pin tooth and a corresponding gear tooth meshing therewith on a same side, is the second point; an end point of the modified recess is located between a third point and a fourth point: when the predetermined pin tooth locates nearest to said meshing instant center, a third meshing point, formed by an adjacent pin tooth and a corresponding gear tooth meshing therewith on the same side, is the third point; and when the predetermined pin tooth locates farthest to said meshing instant center, a fourth meshing point, formed by a pin tooth locating nearest to the meshing instant center and a corresponding gear tooth meshing therewith on the same side, is the fourth point.
 2. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 1, wherein, the starting point of said modified recess is located midway between the first point and the second point.
 3. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 2, wherein, the end point of said modified recess is located midway between the third point and the fourth point.
 4. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 3, wherein, said modified recess is an equi-depth recess of the gear tooth profile of a standard cycloidal pinwheel.
 5. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 4, wherein, a depth of said modified recess is between 0.03 mm and 0.008 mm.
 6. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 5, wherein, a transition between a bottom of the modified recess and the starting point, and a transition between the bottom of the modified recess and the end point, are both smooth arc transitions.
 7. The cycloidal pinwheel pair with uniform contact and one-tooth difference according to claim 4, wherein, a depth of said modified recess is 0.012 mm. 